1. Field of the Invention
The present invention relates to a retrograde display mechanism and a timepiece having the same.
2. Description of the Related Art
In the timepiece, the retrograde display mechanism is used when the tens position (second digit) of a date is displayed by a fan-like or fan-shaped display member in a type in which a date is displayed by a large character (hereinafter, referred to as “big date” type) or when a small hand (hereinafter, referred to as “small day hand”) in the fan-like or fan-shaped display area rotates along the fan (JP-A-2007-218856 (Patent Reference 1) and JP-A-2006-170764 (Patent Reference 2)).
In the retrograde display mechanism, after the fan-like or fan-shaped member is gradually rotated in one direction, when the end of the month is shifted to the beginning of month or when the end of the week is shifted to the beginning of week, the fan-like or fan-shaped member is rapidly rotated reversely to return to an initial position. Therefore, when viewing as a whole, the retrograde display mechanism includes a cam surface of which a diameter increases along one rotation direction as in a spiral, and is provided with a drive cam having a transition surface falling from a spiral maximum diameter portion to a minimum diameter portion and an operating lever which is engaged with an engaged portion of the fan-like or fan-shaped member so as to be elastically pressed against the drive cam through a cam follower on one end side and gradually rotate the fan-like or fan-shaped member in one direction through the engagement portion on the other side. In this case, the operating lever enlarges the position of the cam surface to transmit the position to the engaged portion of the fan-like or fan-shaped member.
However, since there is a limit for the accuracy of the cam surface due to the cost, the position of the fan-like or fan-shaped member is deviated in response to the deviation from an appropriate position of the cam surface, the positions of date and the small day hand in the big date type are shifted, there is concern that the product may look less attractive or that high-class feeling or the like of the external appearance (look) of the product may deteriorate.